Wet sheet for cleaning

ABSTRACT

A wet cleaning sheet  1  has a liquid retentive sheet  12  made of a fibrous material or a cellular material and impregnated with a predetermined amount of a detergent, etc., a liquid impermeable sheet  11  disposed on one side of the liquid retentive sheet  12 , and a liquid gradual-releasing sheet made of a fibrous material and less air permeable than the liquid retentive sheet  12  disposed on the other side of the liquid retentive sheet  12 . The liquid impermeable sheet  11  has a bag shape with openings  13  on one side thereof. The liquid retentive sheet is held in the bag and releases the detergent, etc. through the openings  13 . The liquid gradual-releasing sheet has an air permeability of 0.05 to 6 m/kPa·s thereby to control the gradual release of the detergent, etc.

TECHNICAL FIELD

The present invention relates to a wet cleaning sheet suitable for usein cleaning, polishing or protecting a hard surface. More particularly,it relates to a wet cleaning sheet which releases a large amount of adetergent or a polish to a wide range of surfaces to be cleanedexemplified by floors uniformly from the beginning to the end ofcleaning.

BACKGROUND ART

The present applicant previously proposed a floor cleaning sheetcharacterized by being impregnated with 100 to 1000% by weight, based onthe sheet weight, of an aqueous detergent having a viscosity of 20 to30000 mPa·s at 25° C. (see JP-A-2001-198065). The floor cleaning sheetis typically attached to a mop-like cleaning tool on use. With thisfloor cleaning sheet, the aqueous detergent is slowly released in astable manner, and a wide area can be cleaned with good operationality(ease of use). However, the floor cleaning sheet is mainly contemplatedto be used to wipe off light dust and dirt, such as hairs, soil dust,and dried soy sauce stains, from flooring. Accordingly, the amount ofthe detergent the sheet is designed to release per tatami (“tatami” is a90 cm wide and 180 cm long mat and is used to mean an equivalent area)is as small as 1.6 g or less for first tatami and 0.6 g or less forsecond to nth tatami. In other words, what is aimed at is very slowrelease of a detergent. Such a small amount of the released detergentmay not be seen as enough to remove heavy persistent stains. That amountcan be seen as insufficient particularly in applying a polish. At leastabout 2 g of a polish should be released per tatami stably in order togive a uniform spread of the polish to flooring. Besides, in applyingsuch an agent as a polish, the sheet should have a liquid impermeablelayer on its side to be brought into contact with a mop-like cleaningtool, to which it is attached, so that the cleaning tool may not besoiled.

The present applicant also proposed a detergent-impregnated article(sheet) comprising a detergent retentive layer containing a hydrophobicmaterial and a pair of detergent releasing layers that are denser thanthe detergent retentive layer, the detergent retentive layer being heldin between the detergent releasing layers (see JP-A-10-272082). The mainsubject to which the article is intended to be applied is glass, and thearticle is designed to be hand held. Furthermore, the article ischaracterized in that the release of the detergent is regulated byfolding the sheet. Accordingly, the article is not optimally designed tobe attached to a tool and to slowly release a detergent from only oneside thereof, which is not folded back, to a wide area such as flooring.

The present applicant also proposed a cleaning sheet comprising a wipingpart and a liquid absorbent member which absorbs the liquid wiped upwith the wiping part, the wiping part being a liquid permeable surfacesheet having a large number of projections (see JP-A-9-131288). Theproposed cleaning sheet itself is not impregnated with a detergent. Itis used to carry out cleaning while wiping up a detergent separatelysupplied to a surface to be cleaned.

Apart from these cleaning sheets, JP-U-4-33971 discloses a disposableapplicator comprising a resin film bag with a joint a part of which isadapted to be opened under applied pressure, a liquid to pasty agentsealed into the bag, an agent-impregnated layer disposed on one side ofthe bag, an agent permeation controlling layer provided on theagent-impregnated layer, an agent-permeable wiping layer provided on theagent permeation controlling layer, and an agent-impermeable layerdisposed on the other side of the bag, all these members being joinedtogether. The resin film bag with a joint a part of which is adapted tobe opened under pressure may be replaced with a resin film bag withholes which are sealed with an adhesive film. Since the resin film bagof the applicator is adapted to be opened under pressure, there is afear that the bag is unintentionally opened under some pressure appliedduring preparation, transportation or storage, resulting in leakage ofthe agent. The applicator is not designed to be best suited for slowrelease of a polish, etc. in treating a wide area such as flooring, norfor attachment to a cleaning tool.

An applicator comprising an agent container having an agent sealedtherein, a sealing member attached to the agent container and capable offorming holes in the agent container when removed, and a wiping layerprovided on the sealing member is also known (see JP-A-10-127549 andJP-A-10-262889). In view of the drawback of the applicator ofJP-U-4-33971 supra that the openable film bag containing an agent islikely to be opened unintentionally by pressure application duringpreparation, transportation or storage to leak the agent, theabove-described applicator is characterized by eliminating such atrouble. According to the publication, where the individual holes formedby removing the sealing member have an area of 1 mm² or less, and thetotal opening area is 0.002 to 0.02% of one side area of the container,the applicator releases the agent slowly to have an extended servicelife, supplying the agent uniformly from beginning to end ofapplication. However, where the individual holes are as small as 1 mm²or less, and the total opening area ratio to the area of one side of thecontainer is 0.002 to 0.02%, the applicator is incapable of uniformlyreleasing a large amount of an agent over a wide area to be treated.

Accordingly, an object of the present invention is to provide a wetcleaning sheet capable of releasing a large amount of a detergent or apolish uniformly from the beginning to the end of cleaning to a widearea to be cleaned such as a floor.

DISCLOSURE OF THE INVENTION

The above object of the present invention is accomplished by a wetcleaning sheet includes a liquid retentive sheet made of a fibrousmaterial or a foamed material and impregnated with a predeterminedamount of a detergent or a polish. The liquid retentive sheet has aliquid impermeable sheet on one side thereof and a liquidgradual-releasing sheet on the other side thereof. The liquidgradual-releasing sheet is made of a fibrous material and exhibits anair permeability lower than that of the liquid retentive sheet. Theliquid gradual-releasing sheet has an air permeability of 0.05 to 6m/kPa·s so as to control the gradual release of the detergent or thepolish.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of a wet cleaning sheet according to a firstembodiment of the present invention.

FIG. 2 is a cross-section taken along line II-II in FIG. 1.

FIG. 3 is a perspective of a first member before use.

FIG. 4 is a cross-section taken along line IV-IV in FIG. 1.

FIG. 5 is a perspective showing the wet cleaning sheet of FIG. 1 in use.

FIG. 6 is a perspective of a wet cleaning sheet according to a secondembodiment of the present invention, with a part cut away.

FIG. 7 is a perspective of a wet cleaning sheet according to a thirdembodiment of the present invention, with a part cut away.

FIG. 8 is a perspective of a wet cleaning sheet according to a fourthembodiment of the present invention, with a part cut away.

FIG. 9 is a perspective of a wet cleaning sheet according to a fifthembodiment of the present invention.

FIG. 10 is a cross-section taken along line X-X in FIG. 9.

FIG. 11 is a perspective of a first member before use.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described with reference to its preferredembodiments while referring to the accompanying drawings. FIG. 1 shows aperspective of a wet cleaning sheet according to the present invention(hereinafter sometimes referred to simply as “wet sheet”). The wet sheet1 according to the subject embodiment is suitably used to clean orpolish a hard surface, such as flooring. The wet sheet 1 is composed oftwo members, a first member 10 and a second member 20. Before use thetwo members 10 and 20 are separate from each other.

As shown in FIG. 2, the first member 10 has a liquid impermeable sheet11 and a liquid retentive sheet 12. The liquid impermeable sheet 11 ismade of a liquid impermeable film. The liquid impermeable sheet 11 hasthe shape of a flat bag that is rectangular when viewed from above,having a first side 11 a and a second side 11 b. The bag is formed byjoining two rectangular liquid impermeable sheets 11 at their fouredges. The bag-shaped liquid-impermeable sheet 11 has two openings 13made on a part thereof, specifically on the first side 11 a. Eachopening 13 is an elongated hole extending in the longitudinal directionof the first side 11 a. Each opening 13 is present over the whole areaof the first side 11 a that faces the liquid retentive sheet 12.

The liquid retentive sheet 12 is made of a fibrous material or acellular material and enclosedly held in the bag-shaped liquidimpermeable sheet 11. The liquid retentive sheet 11 has a rectangularshape slightly smaller than the bag-shaped liquid impermeable sheet 11.The liquid retentive sheet 12 is impregnated with a predetermined amountof a detergent or a polish (hereinafter inclusively referred to as “adetergent” unless otherwise noted). The openings 13 each have such asize and/or an area ratio as to allow an adequate amount of a detergentof the liquid retentive sheet 12 to pass therethrough to the whole ofthe liquid gradual-releasing sheet described later. Specifically, thearea of each opening 13 is preferably 5 to 13,000 mm², more preferably 5to 8,700 mm², so as not to hinder release of a detergent. For the samereason, the ratio of the total area of the openings 13 to the liquidretentive sheet-facing area of the first side 11 a, namely, the totalopening area ratio is preferably 1 to 50%, more preferably 3 to 33%,most preferably 3 to 25%.

As shown in FIG. 3, the first member 10 before use has its openings 13closed with a seal 14 as means for sealing so that the detergentimpregnating the liquid retentive sheet 12 may not leak out from thebag. The seal 14 is stripped off to expose the openings on use.

The second member 20 shown in FIG. 1 is a liquid gradual-releasing sheetcomposed of an inner sheet 21 and a surface sheet 22. The liquidgradual-releasing sheet may have either a multi-ply structure as in thepresent embodiment or a single-ply structure. As illustrated in FIG. 4,the two sheets 21 and 22 are superposed on each other and joinedtogether. The inner sheet 21 has a rectangular shape of almost the samesize as the bag-shaped liquid impermeable sheet 11. The surface sheet 22is as long as but wider than the inner sheet 21, laterally extendingfrom both the long sides of the inner sheet 21 to form a pair of flaps23 and 23 of the second member 20. The usage of the flaps 23 will bedescribed infra. As shown in FIG. 4, the four side edges of the innersheets 21 are bonded to the surface sheet 22 into a unitary sheet. Thatis, the liquid gradual-releasing sheet has a two-ply structure.

The liquid gradual-releasing sheet composed of the inner sheet 21 andthe surface sheet 22 is made of a fibrous material similarly to theliquid retentive sheet 12. The liquid gradual-releasing sheet is lesspermeable to air than the liquid retentive sheet 12, however. Airpermeability reduces with a decrease in fiber-to-fiber distance. Thefiber-to-fiber distance being equal, air permeability reduces with anincrease in thickness. The particulars about air permeability will bedescribed later.

The inner sheet 21 has a large number of projections on its surface,whereby to reduce the contact area between the inner sheet 21 and theadjacent upper and lower sheets. As a result, excessive release of adetergent that is liable to occur in the beginning of cleaning issuppressed to improve the gradual releasability. It is desirable thatthe projections be formed over the entire surface of the sheet. Theprojections can be formed by, for example, embossing. Matched steelembossing is especially preferred for shape retention in a wet state.The projections include ridges and domes. The inner sheet 21 of thepresent embodiment have depressions between the projections to have anuneven pattern over the entire area thereof. The depressions and theprojections alternate along both the length and the width of the sheet.The shape of the depressions is an inversion of the projections.

In carrying out matched steel embossing to form projections of the innersheet 21, the emboss pattern is preferably such that the contact areabetween the inner sheet 21 and the adjacent sheet, whether upper orlower, be 5 to 60% of the entire area of the inner sheet 21. This valuewill hereinafter be referred to as a contact area ratio. The height ofthe projections is preferably 0.2 to 10 mm. The cross-sectional shape ofthe projections is preferably a wave form as illustrated in FIG. 4. Thecontact area ratio is measured as follows.

1) Spray glue (3M 55, available from Sumitomo 3M Ltd.) is uniformlysprayed to a measuring part of an inner sheet at a rate of about 0.0006g/cm².

2) Seven kinds of dust for JIS testing (fine particles of the Kantoloam) are uniformly spread on a flat table.

3) The inner sheet was placed on the table with the glue applied sidedown, and a flat acrylic resin plate is put thereon. A weight is put onthe resin plate to give a total load of 500 g (the weight of the resinplate plus the weight of the weight) to the sheet. The inner sheet after5 minute application of the load is used as a sample.

4) The surface of the sample is subjected to image analysis. The ratioof the area soiled with the dust to the area having been in contact withthe table is calculated to obtain a contact area ratio.

It is desirable for the surface sheet 22 to have a large number ofprojections similarly to the inner sheet 21 as shown in FIG. 4 for thesame reason as for the projections of the inner sheet 21. Theprojections of the surface sheet 22 can be configured similarly to thoseof the inner sheet 21 in terms of contact area ratio, shape, and thelike.

In using the wet sheet of the present embodiment, the second member 20is disposed on the first member 10 with the inner sheet 21 of the formerfacing the first side 11 a of the latter where openings 13 are made asshown in FIG. 1. The wet sheet 1 in this state is attached to thecleaning tool 30 shown in FIG. 5. The cleaning tool 30 is composed of aflat cleaning part 31, to which the wet sheet 1 is to be attached, and ahandle 33 of stick form which is rotatably connected to the cleaningpart 31 through a universal joint 32. The cleaning part 31 has arectangular shape of almost the same size as the first member 10. Thewet sheet 1 is attached to the cleaning part 31 with its second side 11b (see FIG. 2) in contact with the lower side of the cleaning part 31.The flaps 23 and 23 of the second member 20 are folded back on the upperside of the cleaning part 31. The upper side of the cleaning part 31 isprovided with flexible members 34 each having radial slits. The flaps 23are pressed into the slits and thereby fixed to the cleaning part 31.The wet sheet 1 is thus ready to be used to clean a floor, etc.

Being so configured, the wet sheet 1 according to the above-describedembodiment offers the following advantages. Firstly, since the firstmember 10 and the second member 20 are separate, and the liquidretentive sheet 12 impregnated with a detergent is contained in abag-shaped liquid impermeable sheet 11 and the sheet 11 is air-tightlysealed, it is possible for the liquid retentive sheet 12 to retain alarge quantity of a detergent. Sealed in the liquid impermeable sheet11, the liquid retentive sheet 12 is prevented from soiling a user'shand when in attaching the wet sheet 1 to the cleaning tool 30. As amatter of course, the cleaning tool 30 is not soiled, either. Thedetergent is prevented from leaking while stored before use. On use, theseal 14 is stripped off to expose the openings 13, whereby the detergentis released out of the bag, being no more blocked at the openings 13.The detergent released through the openings 13 is once held by theliquid gradual-releasing sheet having low air permeability, i.e., asmall fiber-to-fiber distance and high capillarity, and then graduallyreleased therefrom toward the surface to be cleaned. Therefore, therelease of the detergent is kept almost constant from the very beginningto the end of a cleaning operation. Since both the inner sheet 21 andthe surface sheet 22 constituting the liquid gradual-releasing sheethave projections and depressions, the contact area with the surface tobe cleaned is reduced, which also serves for gradual release of thedetergent. With the liquid retentive sheet 12 containing a large amountof the detergent, the wet sheet is capable of sufficiently cleaning awide surface such as a floor. In short, the release of the detergent iscontrolled not by adjusting the size and/or the open area ratio of theopenings 13 but by using a liquid gradual-releasing sheet having aspecifically controlled air permeability.

The members making up the wet sheet 1 of the present embodiment willthen be described. The liquid impermeable sheet 11 of the first member10 can be of any material that is soft to some extent and impermeable toliquid. For example, a thermoplastic resin film or a thermoplastic resinfilm laminated with a vacuum deposited thin film of a metal such asaluminum can be used as the liquid impermeable sheet 11.

The liquid retentive sheet 12 is made of a fiber aggregate or a cellularmaterial as stated. It is desirable that the liquid retentive sheet 12be capable of holding a large quantity of a detergent and exhibitexcellent detergent releasability. Suitable fibrous materials includefiber aggregates, such as bulky paper and nonwoven fabric, particularlyair-laid nonwoven fabric and needle-punched nonwoven fabric. The fiberincludes natural fibers, chemical fibers, and mixtures thereof. Thenatural fibers include wood pulp, and the chemical fibers includeregenerated fibers, as exemplified by rayon and acetate, and syntheticfibers, such as polyolefin fibers as exemplified by polyethylene andpolypropylene, polyester fiber, polyamide fiber as exemplified by nylon,and polyacrylonitrile fiber. Suitable cellular materials include thoseobtained by foaming or porosification by making use ofchemical-reaction-induced gas bubbles or by injecting a low meltingsolvent, e.g., Freon gas, or air, as exemplified by polyurethane foamand polyolefin foam.

The liquid retentive sheet 12 is more air permeable than the liquidgradual-releasing sheet. Specifically the air permeability of the liquidretentive sheet 12 is preferably 10 to 70 m/kPa·s, more preferably 15 to40 m/kPa·s. The air permeability was measured on a detergent-free samplewith an air permeability tester KES-F8-AP1 supplied by Kato Tech Co.,Ltd.

In order for the liquid retentive sheet 12 to have an increased capacityof retaining a detergent and to secure satisfactory release of thedetergent while in use, the liquid retentive sheet 12 preferably has adensity of 0.02 to 0.2 g/cm³, more preferably 0.03 to 0.15 g/cm³. Thebasis weight of the liquid retentive sheet 12 is preferably 20 to 400g/m², more preferably 60 to 200 g/m². Within that range of basis weight,the liquid retentive sheet 21 has good fabricability and sufficientliquid retention capacity.

While it is desirable that the liquid retentive sheet 12 be impregnatedwith as large an amount of a detergent as possible, a usual amount of adetergent to be infiltrated would be about 300 to 3000%, particularlyabout 500 to 2500%, based on the dry weight of the liquid retentivesheet, assuming that a floor in a common house is cleaned with a singlewet sheet 1.

The liquid gradual-releasing sheet of the second member 20 is made of afibrous material similarly to the above-mentioned liquid retentive sheet12. The liquid gradual-releasing sheet is a single ply sheet made of afibrous material or a laminate (multiply) sheet composed of two or moreplies made of a fibrous material. The detergent released from the liquidretentive sheet 12 is once diffused throughout the liquidgradual-releasing sheet and then delivered from the liquidgradual-releasing sheet to a wide area to be cleaned at a rate lowerthan that of the release from the liquid retentive sheet 12. Thus, theliquid gradual-releasing sheet serves to gradually release the detergentin an amount within a prescribed range from the beginning to the end ofcleaning. For this purpose, the liquid gradual-releasing sheet is madeless air permeable than the liquid retentive sheet 12. In other words,air permeability is a measure of gradual releasability of a detergent inthe present invention. It is a fact first found by the present inventorsthat the air permeability of a sheet is correlative to gradualreleasability. In order to control the rate of releasing a detergentwithin an appropriate range, the air permeability of the liquidgradual-releasing sheet ranges 0.05 to 6 m/kPa·s, preferably 0.1 to 4m/kPa·s, more preferably 0.1 to 3 m/kPa·s.

The void structure of the liquid gradual-releasing sheet is ofimportance for air permeability control. For instance, a sheet withvoids of smaller size or with a smaller number of voids has lower airpermeability to release a lower amount of the detergent. That is, thefactors for controlling air permeability include the void structure, thebasis weight, the number of plies, etc. of the sheet. Whether the liquidgradual-releasing sheet has a single- or a multi-ply structure, thesheet should be prevented from retaining too much detergent so that itcan release a large amount of the detergent gradually and uniformly.From this viewpoint, the basis weight of the liquid gradual-releasingsheet is preferably 20 to 350 g/m², more preferably 40 to 200 g/m².

Materials that satisfy the aforethe air permeability include fibersheets, such as wet process paper, spun laced nonwoven fabric, and meltblown nonwoven fabric. The void structure of wet process paper can beregulated by selecting fiber, adjusting the freeness, wet pressure(pressure applied before drying), and calendering pressure (pressureapplied after drying), adding a loading filler, and like means. Thefibers of options include soft wood pulp, hard wood pulp, variousmodified pulps, rayon fiber, and thermoplastic resin fibers. Choosingfiner fiber or shorter fiber results in smaller void sizes (diameters)and lower air permeability. Increasing the degree of beating (freeness),the wet pressure or the calendering pressure also results in smallervoid sizes and lower air permeability. Increasing the amount of thefiller also brings about reduction in size or number of voids, leadingto reduction of air permeability. In using spun laced nonwoven fabric,the size of the voids is decreased to reduce air permeability by, forexample, using hydrophilic fiber, such as cotton or rayon, using fiberhaving a small thickness, or increasing the entanglement density. Wherethe liquid gradual-releasing sheet is to be embossed, it is advisable touse a sheet containing 5 to 95% by weight, particularly 10 to 75% byweight, of thermoplastic fiber, which is easier to heat-emboss to formprojections that are retainable even when wet.

Where the liquid gradual-releasing sheet has a laminate structurecomposed of the inner sheet 21 and the surface sheet 22 as in thepresent embodiment, there are an advantage that the cleaningoperationality is improved further and an advantage that the inner sheet21 is protected. There is also offered an advantage that the release ofthe detergent is controlled further. As previously described, thesurface sheet 22 has a large number of projections on its cleaning sideso as to have improved cleaning operationality. By this surfaceunevenness, the contact area with a surface to be cleaned reduces toreduce the friction on wiping, which also improves cleaningoperationality. The constituent fiber used to make the surface sheet 22and the shape of the projections of the surface sheet 22 can be the sameas those described in JP-A-9-131288.

The inner sheet 21 and the surface sheet 22 may be made of the same ordifferent materials. As long as the basis weight of the liquidgradual-releasing sheet falls within the above-recited range, it ispreferred for the surface sheet 22 to have a basis weight ranging 10 to100 g/m², particularly 20 to 80 g/m², in order to secure sufficientsheet strength for cleaning and incur no more cost than necessary.

The detergent and the polish to be infiltrated into the liquid retentivesheet will then be described. The detergent used in the presentinvention is for dissolving and wiping off dust and dirt that are hardto remove by dry cleaning, such as soil dust, sebum, and grease. Thepolish is for giving a shine and a protection to flooring. The polishmay have a cleaning function as well. For satisfactory spreadability andgood finish, the detergent and the polish preferably have a viscosity of1 to 20 mPa·s, more preferably 2 to 10 mPa·s, at 25° C. The viscositywas measured with a Brookfield viscometer supplied by Tokyo Keiki K.K.(rotor No. 1, 60 rpm). The detergent preferably contains water as amedium, a surface active agent, an alkali agent, and a water-solublesolvent. The polish includes commercially available polishes satisfyingthe above-recited viscosity condition. The compositions disclosed inJP-A-2001-131495 filed by the present applicant can be mentioned asexamples. The detergent or polish is preferably applied to a surface tobe treated in an amount of 1.5 to 8 g/tatami, more preferably 2 to 6g/tatami (tatami≈1.6 m²).

The surface active agent used in the detergent includes anionic,nonionic, cationic, and amphoteric ones. From the standpoint of cleaningability and finish, suited are nonionic surface active agents, such aspolyoxyalkylene (number of moles of alkylene oxide: 1 to 20) C8-C22alkyl (straight-chain or branched) ethers, C8-C22 alkyl (straight-chainor branched) glycosides (average degree of sugar condensation: 1 to 5),sorbitan C8-C22 fatty acid (straight-chain or branched) esters, andC6-C22 alkyl (straight-chain or branched) glycerol ethers; andamphoteric ones, such as alkylcarboxybetaines, alkylsulfobetaines,alkylhydroxysulfobetaines, alkylamidocarboxybetaines,alkylamidosulfobetaines, and alkylamidohydroxysulfobetaines, each having8 to 24 carbon atoms in the alkyl moiety thereof. From the viewpoint ofcleaning ability and finish, a preferred content of the surface activeagent in the detergent is 0.01 to 1.0% by weight, particularly 0.05 to0.5% by weight.

The alkali agent which can be used in the detergent includes hydroxides,e.g., sodium hydroxide, carbonates, e.g., sodium carbonate, alkalinesulfates, e.g., sodium hydrogensulfate, phosphates, e.g., sodium primaryphosphate, organic alkali metal salts, e.g., sodium acetate and sodiumsuccinate, ammonia, alkanolamines, e.g., mono-, di- or triethanolamine,β-aminoalkanols, e.g., 2-amino-2-methyl-1-propanol, and morpholine.Alkanolamines, e.g., mono-, di- or triethanolamine, β-aminoalkanols,e.g., 2-amino-2-methyl-1-propanol, and morpholine are preferred in viewof the feel and pH buffering action. A suitable content of the alkaliagent in the detergent is 0.01 to 1% by weight, preferably 0.05 to 0.5%by weight, from the standpoint of cleaning ability and feel.

The water-soluble solvent used in the detergent is suitably one or moreselected from monohydric alcohols, polyhydric alcohols, and derivativesthereof. Those having a vapor pressure of 267 Pa (2 mmHg) or higher areparticularly preferred in view of finish. For example, ethanol,isopropyl alcohol, propanol, ethylene glycol monomethyl ether, propyleneglycol monomethyl ether, etc. are preferred. A suitable water-solublesolvent content in the detergent is 1 to 50% by weight, preferably 1 to20% by weight, from the viewpoint of smell and low skin irritation.

The detergent can contain an antimicrobial agent in addition to theabove-described components thereby to endow the detergent with anantimicrobial effect in addition to the cleaning effect. Usefulantimicrobial agents include hydrogen peroxide, hypochlorous acid,sodium hypochlorite, quaternary ammonium salts, sodium benzoate, sodiump-hydroxybenzoate, and natural antimicrobials. Quaternary ammonium saltsand polylysine (natural antimicrobial agent), etc. are particularlypreferred in view of their compounding stability and antimicrobialactivity. A suitable content of the antimicrobial agent in the detergentis 0.005 to 2% by weight, particularly 0.01 to 1% by weight, taking intoconsideration the balance between the antimicrobial effect and low skinirritation.

The detergent, etc. can further contain perfumes, antifingals, colorants(dyes and pigments), chelating agents, waxes, and so forth according tonecessity.

The content of water, a medium of the detergent, is preferably 50 to99.9% by weight, more preferably 80 to 99% by weight, in view of thefinish of the cleaned surface.

Second to fourth embodiments of the present invention will be describedby way of FIGS. 6 through 8. The second to fourth embodiments will bedescribed only with reference to differences from the first one. Thedescription with respect to the first embodiment appropriately appliesto the particulars that are not mentioned here. The members in FIGS. 6to 8 that are the same as those in FIGS. 1 through 5 are given the samerespective reference numbers.

The wet sheet 1 of the second embodiment shown in FIG. 6 is an integralarticle unlike the wet sheet of the first embodiment. The wet sheet 1has a liquid retentive sheet 12 made of a fibrous material andimpregnated with a detergent. On one side of the liquid retentive sheet12 is disposed a liquid impermeable sheet 11. On the other side isdisposed a liquid gradual-releasing sheet composed of an inner sheet 21and a surface sheet 22, both of which are made of a fibrous material.The liquid gradual-releasing sheet is less permeable to air than theliquid retentive sheet 12. A liquid impermeable sheet 24 having twoopenings 13 is provided between the liquid retentive sheet 12 and theliquid gradual-releasing sheet.

The liquid retentive sheet 12 has a rectangular shape and is placed onthe liquid impermeable sheet 11. The liquid impermeable sheet 11 extendslaterally from both the long sides of the liquid retentive sheet 12 toform a pair of flaps 23 and 23. The inner sheet 21 is a rectangle of thesame size as the liquid retentive sheet 12 and is disposed on the liquidretentive sheet 12. The surface sheet 22 is slightly larger than theliquid retentive sheet 12 and the inner sheet 21, extending outward fromthe four edges of these two lower sheets. The liquid impermeable sheet24 is of almost the same shape and size as the surface sheet 22. Theextensions of the liquid impermeable sheet 24 are bonded to the liquidimpermeable sheet 11. The liquid retentive sheet 12 and the inner sheet21 are thus enclosed in the space formed by the liquid impermeable sheet11 and the liquid impermeable sheet 24. Both the inner sheet 21 and thesurface sheet 22 are provided with projections or depressions.

The openings 13 formed through the liquid impermeable sheet 24 have thesame shape as the elongated openings formed through the bag-shapedliquid impermeable sheet 11 of the first embodiment. The openings 13 areclosed with respective strip seals 14 so that the detergent impregnatingthe liquid retentive sheet 12 may not leak. One end of each seal 14extends outward from an edge of the wet sheet 1. In using the wet sheet1, the seals 14 are pulled out to expose the openings 13.

The wet sheet 1 of the second embodiment is used as attached to thecleaning tool 30 shown in FIG. 5 with the outer surface of the liquidimpermeable sheet 11 in contact with the lower side of the cleaning part31 of the cleaning tool 30. According to this embodiment, it is possibleto have a large amount of a detergent infiltrated into the liquidretentive sheet 12 because the detergent-impregnated liquid retentivesheet 12 is enclosed in the space formed by the liquid impermeable sheet11 and the liquid impermeable sheet 24. Similarly to the firstembodiment, neither user's hands nor the cooling tool 30 is soiled whenthe wet sheet 1 is fixed to the cleaning tool 30. The amount of thedetergent released is maintained substantially constant from thebeginning to the end of cleaning. A large amount of the detergent beingretained in the liquid retentive sheet 12, the wet sheet 1 is capable ofsufficiently cleaning a wide area such as a floor.

The wet sheet 1 according to the third embodiment shown in FIG. 7corresponds to the wet sheet of the second embodiment shown in FIG. 6from which the liquid impermeable sheet 24 and the seals 14 closing theopenings 13 of the sheet 24 are removed. The wet sheet 1 according tothe fourth embodiment shown in FIG. 8 corresponds to the wet sheet ofthe second embodiment shown in FIG. 6 from which the seals 14 closingthe openings 13 of the liquid impermeable sheet 24 are removed. In thesewet sheets, the release of the detergent is controlled by adjusting theair permeability of the liquid gradual-releasing sheet as in the firstand second embodiments. Unlike the first and second embodiments,however, the wet sheets of the third and fourth embodiments have apossibility that the detergent may ooze out through the inner sheet 21and the surface sheet 22 under some storage conditions of the wet sheet1. In such a case, it is desirable that each wet sheet 1 or a few wetsheets 1 be pillow packaged in a liquid impermeable sheet bag forstorage.

The fifth embodiment of the present invention will be described byreferring to FIGS. 9 through 11. The fifth embodiment will be describedonly with regard to differences from the first one. The description ofthe first embodiment applies appropriately to the particulars notmentioned here. The members in FIGS. 9 to 11 that are the same as thosein FIGS. 1 through 5 are given the same respective reference numbers.

As shown in FIG. 9, the first member 10 has a container 111 and a liquidretentive sheet 12 held in the container 111. The liquid retentive sheet12 is contained in the container 111 that is a flat bag and thecontainer 111 is air-tightly sealed. The liquid retentive sheet 12 has arectangular shape slightly smaller than the container 111.

The container 111 is formed of a first liquid impermeable sheet 11 a anda second liquid impermeable sheet 11 b, both of which are laminatesheets composed of a uniaxially stretched film and a metal foil. The twoliquid impermeable sheets 11 a and 11 b are of the same kind and of thesame size, both having an elongated rectangular shape when seen from theabove. The container 111 is formed by bonding the four edges of twosuperposed liquid impermeable sheets 11 a and 11 b into a bag shape. Thestretching direction of the uniaxially stretched film agrees with thelongitudinal direction of the liquid impermeable sheets 11 a and 11 b.

The materials of the liquid impermeable sheets 11 a and 11 b, which formthe container 111, are not particularly limited as long as the sheetsare flexible to some extent and impermeable to liquid. For example, athermoplastic resin film or a thermoplastic resin film laminated with athin metal (e.g., aluminum) film by vacuum evaporation can be used asthe liquid impermeable sheets 11 a and 11 b as mentioned above. The twoliquid impermeable sheets 11 a and 11 b may be either of the same ordifferent kinds. Note that, however, at least the first liquidimpermeable sheet 11 a, which faces the liquid gradual-releasing sheet21, should have a layer of a uniaxially stretched film.

As illustrated in FIG. 10, the first liquid impermeable sheet 11 a,which is to face the second member 20, has two guiding portions foreasy-open or easy-to-open portions 141 having a prescribed width andextending in the stretching direction of the uniaxially stretched film.Each of the easy-to-open portions 141 is formed by superposing a stripof a sheet material on the first liquid impermeable sheet 11 a.Accordingly the easy-to-open portions 141 have a higher basis weight andhigher strength than the other part of the first liquid impermeablesheet 11 a. A uniaxially stretched film is known mechanically strong inthe stretching direction but less strong in the direction perpendicularto the stretching direction. Seeing that the stretching direction of theuniaxially stretched film in the present embodiment is the same as thelongitudinal direction of the first liquid impermeable sheet 11 a asnoted above, the first liquid impermeable sheet 11 a is mechanicallystronger in the length than in the width and therefore easy to tearalong the borders of the easy-to-open portions 141.

The easy-to-open portions 141 are provided over substantially the wholelength of the container 111. The easy-to-open portions 141 each have atab 151 at one end thereof. A part of the first liquid impermeable sheet11 a serves as the tab 151. The tab 151 is formed by making that part ina state non-bonded to the first liquid impermeable sheet 11 a. The tab151 is a portion providing a starting point for tearing off theeasy-to-open portion 141 from the other part of first impermeable sheet11 a. The tab 151 is pinched with the fingertips and pulled toward theother end of the easy-to-open portion 141 thereby to tear apart thatportion of the first liquid impermeable sheet 11 a and to make anopening 13. At the root of the tab 151 the first and second liquidimpermeable sheets 11 a and 11 b are bonded together over the width ofthe container 111 to form a joint 16. The joint 16 is provided in orderthat the detergent impregnating the liquid retentive sheet 12 may notooze outside from the root of the tabs 151 during storage of thecontainer 111.

Before use of the wet sheet 1, the first liquid impermeable sheetinclusive of the easy-to-open portions 141 is in an untorn state, andthe liquid retentive sheet 12 held in the container 111 is thus kept ina sealed state. On use, each of the tabs 151 is pinched with thefingertips, pulled up to separate the bonded first and second liquidimpermeable sheets 11 a and 11 b apart, and pulled further to tear offthe easy-to-open portion 141 of the first liquid impermeable sheet inthe stretching direction of the sheet as depicted in FIG. 11. By sodoing, openings 13 having substantially the same shape of theeasy-to-open portions 141 are made in the first liquid impermeable sheet11 a, thereby allowing the detergent infiltrated into the liquidretentive sheet 12 to be released from the openings 13.

According to the fifth embodiment, the liquid retentive sheet 12 is keptsealed until immediately before use of the wet sheet 1. The liquidretentive sheet 12 is released from the sealed state for the first timewhen the easy-to-open portions 141 are torn off in the stretchingdirection on use. Therefore, a large quantity of a detergent, etc. canbe held infiltrated into the liquid retentive sheet 12 without beingleaked or evaporated. Unlike the applicator disclosed in JP-A-10-127549supra, since the wet sheet 1 of the present embodiment needs no sealingmember for blocking the openings of a container having an agent sealedtherein, it enjoys good productivity and realizes reduction inproduction cost.

According to the fifth embodiment, although the wet cleaning sheet has acontainer having sealed therein a large amount of an agent such as adetergent and a polish, it is free from the leakage problem that mayoccur during the preparation, transportation or storage. On use, aprescribed opening can easily be made in the container to supply a largequantity of a polish, etc. to a wide area such as a floor uniformly fromthe beginning to the end of cleaning. In addition, the wet cleaningsheet of the embodiment is produced with good productivity, leading to areduction of the production cost.

While the present invention has been described with respect to thepreferred embodiments thereof, it should be understood that theinvention is not deemed limited thereto. For example, another sheet orsheets may be superposed on the outer side of the liquidgradual-releasing sheet for the purpose of protecting the liquidgradual-releasing sheet or improving the operationality of the wetsheet.

The inner sheet 21 and/or the surface sheet 22 used in theabove-described embodiments do not always need to have projections.

While in the fifth embodiment part of the first liquid impermeable sheet11 a is made into easy-to-open portions by superposing strips of a sheetmaterial, some kinds of a uniaxially stretched film need no sucheasy-to-open portions except pull tabs of prescribed width. In thiscase, an opening can be made in the first liquid impermeable sheet 11 asimply by pulling the pull tab in the stretching direction of the film.

While in the fifth embodiment the easy-to-open portions 141 are formedby superposing strips, they can be formed by mechanically drawing linesby laser processing or with a tool, along which the sheet is tearable.By this method even a liquid impermeable sheet containing a lesstearable uniaxially stretched film can be made easily tearable.

While in the fifth embodiment the tab 151 at one end of the easy-to-openportion 141 is in a non-bonded state to the second liquid impermeablesheet 11 b, the tab 151 may be bonded lightly such that it can be peeledwith a fingertip.

The wet sheet 1 of the present invention is fit especially for cleaningflooring. It is also suitable for cleaning or polishing other hardsurfaces, such as car bodies and leather shoes.

In Examples hereinafter given all the percents are by weight unlessotherwise noted.

EXAMPLE 1

A 80 mm wide and 250 mm long sheet of air laid nonwoven fabric(material: soft wood kraft pulp/thermoplastic fiber (heat fusiblepolyester fiber)/latex binder=52/34/14 by weight; basis weight: 140g/m²; density: 0.05 g/cm³; air permeability: 10.3 m/kPa·s) was used as aliquid retentive sheet. The liquid retentive sheet was impregnated with1430% of a cleaning polish (Tsuyadashi Mypet (trade name) available fromKao Corp.; viscosity (25° C.): 4 mPa·s).

Two aluminum deposited sheets having a thickness of 49 μm were used asliquid impermeable sheets. Two elongated holes each of 7.5 mm in widthand 210 mm in length were punched out of one of the sheets, and theopenings were covered with an adhesive aluminum deposited sheet. Thecleaning polish-impregnated liquid retentive sheet was sandwiched inbetween the two sheets, and the four edges of the two sheets were heatsealed to prepare a 95 mm wide and 270 mm long package with openings(open area ratio of the elongated holes: 12.3%).

Two sheets of paper with a basis weight of 30 g/m² fabricated by usualwet papermaking from a mixed fiber material (soft wood kraftpulp/thermoplastic fiber (heat fusible polyester fiber)=90/10 by weight)were superposed on each other and joined together by embossing throughmatched steel rollers to prepare an inner sheet having projections. Theresulting inner sheet had an air permeability of 0.3 m/kPa·s. A sheet ofpaper having a basis weight of 12 g/m² was prepared by wet papermakingfrom a mixed fiber material (soft wood kraft pulp/heat shrinkable fiber(polypropylene (core)/polyethylene (sheath) conjugatefiber)/thermoplastic fiber (heat fusible polyester fiber)=30/60/10 byweight) and applying a hydrophilizing agent to the fiber layer duringthe step of drying. The paper was superposed on spun bonded nonwovenfabric fabricated of polyester (core)/polyethylene (sheath) conjugatefiber to obtain a composite sheet having a basis weight of 40 g/m²,which was embossed through matched steel rollers to prepare a surfacesheet. The resulting surface sheet had an air permeability of 6.8m/kPa·s. The surface sheet and the inner sheet were combined as shown inFIG. 4 to form a liquid gradual-releasing sheet.

The package having openings was put on the liquid gradual-releasingsheet with the side having the openings facing the inner sheet of theliquid gradual-releasing sheet to make a wet sheet having the structureshown in FIG. 1. The wet sheet was attached to a cleaning tool shown inFIG. 5 and used for cleaning.

EXAMPLE 2

A wet sheet was prepared in the same manner as in Example 1, except forthe following. The inner sheet used in Example 1 was replaced with twothicknesses of paper which had a basis weight of 30 g/m² and wasprepared by usual wet papermaking from a mixed fiber material of softwood kraft pulp/thermoplastic fiber (heat fusible polyester fiber)=90/10by weight. The resulting two-ply inner sheet was used as such withoutembossing. The inner sheet had an air permeability of 0.3 m/kPa·s.

EXAMPLE 3

A wet sheet was prepared in the same manner as in Example 1, except forthe following. The inner sheet used in Example 1 was replaced with twothicknesses of paper which had a basis weight of 30 g/m² and wasprepared from a mixed fiber material of soft wood kraftpulp/thermoplastic fiber (heat fusible polyester fiber)=90/10 by weightunder papermaking conditions different in degree of beating, wetpressure, etc. from those adopted in Example 1 so that the resultinginner sheet might have an air permeability of 0.7 m/kPa·s. The resultinginner sheet was used as such without embossing.

EXAMPLE 4

A wet sheet was prepared in the same manner as in Example 1, except forthe following. The inner sheet used in Example 1 was replaced with twothicknesses of paper which had a basis weight of 40 g/m² and wasprepared from 100% soft wood kraft pulp under papermaking conditionsdifferent in degree of beating, wet pressure, etc. from those adopted inExample 1 so that the resulting inner sheet might have an airpermeability of 5.3 m/kPa·s.

COMPARATIVE EXAMPLE 1

A wet sheet was prepared in the same manner as in Example 1, except thatthe inner sheet was not used. The liquid gradual-releasing sheet ofComparative Example 1 was a single ply sheet.

COMPARATIVE EXAMPLE 2

A wet sheet was prepared in the same manner as in Example 1, except forreplacing the inner sheet used in Example 1 with a single sheet of paperhaving a basis weight of 30 g/m² that was prepared from a mixed fibermaterial of soft wood kraft pulp/thermoplastic fiber (heat fusiblepolyester fiber)/microfibrillated cellulose (Celish KY-100SJ, a tradename, available from Daicel Chemical Industries, Ltd.)=50/10/40(effective content ratio by weight) by a manual wet papermakingtechnique. The resulting inner sheet was used as such without embossing.The inner sheet had an air permeability of 0.04 m/kPa·s.

COMPARATIVE EXAMPLE 3

A wet sheet was prepared in the same manner as in Example 1, except forusing no inner sheet and replacing the elongated holes of the aluminumdeposited sheet with a number of regularly arranged circular holes of 1mm in diameter to provide a total open area ratio of 0.018%.

Evaluation of Performance:

The wet sheets prepared in Examples and Comparative Examples wereevaluated for gradual liquid releasability, capacity of cleaning, andcleaning finish in accordance with the following methods. The resultsobtained are shown in Table 1 below.

1) Amount of Release

A floor of Woody Tile F type KER525F (from Matsushita Electric Works,Ltd.) was continuously wiped with the wet sheet attached to a cleaningtool Quickle Wiper produced by Kao Corp. The amount of liquid releasedper tatami was calculated by weighing the wet sheet detached from thecleaning part of the cleaning tool every time it was used to wipeone-tatami area (90 cm×180 cm). Cleaning per tatami was completed bygiving a 90 cm double stroke (forward and backward) of the cleaning toolto each of eight divided sections (i.e., 2 sections in the lengthdirection by 4 sections in the width direction).

2) Finish

The same wiping operation as in (1) above was conducted, and the finishof the floor after drying was evaluated with the naked eye.

If an agent, particularly a polish, is released too much, the surfacetreated in the initial stage of wiping becomes too sheeny compared withthe finish in the final stage, resulting in noticeable variation ofgloss from place to place. Besides, a polish released too much takestime to dry. On the other hand, if the release of an agent, particularlya polish is too slow, the wet sheet fails to uniformly wet the surfaceto be treated, resulting in gloss unevenness. Therefore, the finish wasevaluated according to the following standard taking the differencedepending on the released amount into consideration.

A: Given a uniform coating, the floor has uniform gloss.

B: Given a non-uniform coating, the floor has uneven gloss with highgloss and low gloss parts.

C: Intermediate between A and B. TABLE 1 Example Comparative Example 1 23 4 1 2 3 Liquid Retentive Air Permeability 10.3 Sheet (m/kPa · s)Density (g/cm³) 0.05 Material air laid nonwoven fabric Impregnation (%)1430 with Agent Liquid Impermeable Opening Area 7.5 mm × 210 mm × 2holes 0.79 mm² Sheet Open Area Ratio (%) 12.3 0.018 Surface SheetContact Area (%) 17 Composition pulp/synthetic fiber = 30/70 (embossed)(weight ratio) Inner Sheet Material wet process paper none wet processNone embossed non- non- non- paper (non- embossed embossed embossedembossed) Liquid gradual- Air Permeability 0.3 0.3 0.7 3.3 6.8 0.04 6.8Releasing Sheet (m/kPa · s) Amount of Release 1st tatami 4.8/a 6.1/b7.1/b 7.7/b 9.2/c 3.0/a 3.0/c (g/tatami)/Finish 2nd tatami 3.5/a 3.1/a3.5/a 6.3/b 5.2/a 1.9/b 1.5/c 3rd tatami 3.3/a 2.6/a 3.9/a 5.0/a 4.1/a1.5/b 1.0/c 4th tatami 3.0/a 2.5/a 2.9/a 3.7/a 3.0/a 1.7/b 0.7/c 5thtatami 2.8/a 2.6/a 2.6/a 2.6/a 2.2/a 1.6/b 0.6/c 6th tatami 2.5/a 2.3/a2.3/a 2.0/a 1.6/b 1.4/c 0.5/c 7th tatami 2.3/a 1.8/b 1.8/b 1.6/b 1.2/c1.0/c 0.5/c Remark noticeable difference in streaky gloss between 1sttatami unevenness in and the rest of the floor 1st tatami

As is apparent from the results in Table 1, it is seen that the wetsheets of Examples according to the present invention release asufficient amount of the liquid even in the stage of cleaning theseventh tatami with a small reduction in amount of release with wipingarea and give a satisfactory finish to the floor. In contrast, becausethe wet sheet of Comparative Example 1 releases too much while wipingthe first tatami, it provides a higher gloss to the first tatami thanthe second and following tatami areas, resulting in unevenness of gloss.It is also seen that the wet sheet of Comparative Example 1 shows agreat reduction in amount of release, failing to achieve cleaning of theseventh tatami area. Although the wet sheet of Comparative Example 2shows a small reduction in amount of release, it is incapable ofcleaning a wide area and provides a poor finish. The wet sheet ofComparative Example 3 releases only a small amount of the liquid fromthe beginning of wiping because the release from the liquid retentivesheet is hindered by the holes. The insufficient release also results inuneven and streaky application of the liquid.

INDUSTRIAL APPLICABILITY

The wet cleaning sheet of the present invention releases a large amountof a detergent or a polish to a wide area such as a floor stably anduniformly from the beginning to the end of cleaning. In applying apolish, in particular, the wet cleaning sheet provides the whole wipedarea with a uniform gloss.

1. A wet cleaning sheet comprising a liquid retentive sheet made of afibrous material or a foamed material and impregnated with apredetermined amount of a detergent or a polish, the liquid retentivesheet having a liquid impermeable sheet on one side thereof and a liquidgradual-releasing sheet on the other side thereof, the liquidgradual-releasing sheet being made of a fibrous material and exhibitingan air permeability lower than that of the liquid retentive sheet,wherein the liquid gradual-releasing sheet has an air permeability of0.05 to 6 m/kPa·s so as to control the gradual release of the detergentor the polish.
 2. The wet cleaning sheet according to claim 1, whichfurther comprises a sheet with an opening having an area of 5 to 13,000mm² interposed between the liquid retentive sheet and the liquidgradual-releasing sheet, the sheet with an opening having an open arearatio of 1 to 50% based on the area facing the liquid retentive sheet.3. The wet cleaning sheet according to claim 2, wherein the opening isin a closed state with a prescribed sealing means and is adapted to bereleased from the closed state on use of the wet cleaning sheet.
 4. Thewet cleaning sheet according to claim 3, wherein the liquid impermeablesheet has a shape of bag, the bag is provided with the opening at a partthereof, the liquid retentive sheet is held in the bag-shaped liquidimpermeable sheet, and the liquid gradual-releasing sheet is arranged soas to face the opening-formed side of the bag-shaped liquid impermeablesheet.
 5. The wet cleaning sheet according to claim 4, wherein theliquid gradual-releasing sheet and the bag-shaped liquid impermeablesheet are separate from each other before use.
 6. The wet cleaning sheetaccording to claim 1, wherein the liquid gradual-releasing sheet hasprojections and depressions.
 7. The wet cleaning sheet according toclaim 1, wherein the detergent or the polish impregnated in the liquidretentive sheet has a viscosity of 1 to 20 mPa·s at 25° C.
 8. The wetcleaning sheet according to claim 1, wherein the liquid retentive sheetis contained in a bag comprising the liquid impermeable sheet whichcontains a uniaxially stretched film layer, the bag being air-tightlysealed, the liquid gradual-releasing sheet is arranged on the side ofthe liquid impermeable sheet which contains the uniaxially stretchedfilm layer, the liquid impermeable sheet which contains the uniaxiallystretched film layer has a tab for starting tearing the uniaxiallystretched film layer in the stretching direction to form an opening. 9.The wet cleaning sheet according to claim 8, wherein the tab is formedof part of the uniaxially stretched film.
 10. The wet cleaning sheetaccording to claim 8, wherein the liquid impermeable sheet whichcontains the uniaxially stretched film layer has a guiding part foreasy-open which has a prescribed width and extends in the stretchingdirection of the uniaxially stretched film layer.